a. Field of the Invention
The present invention relates generally to medical systems for performing therapeutic functions, such as, for example, ablation procedures. More particularly, the present invention relates to an ablating tool having a deployable ultrasound imaging transducer for use in guiding and monitoring ablation procedures; and methodologies of monitoring and/or assessing the performance of such ablation procedures.
b. Background Art
It is known to use minimally invasive surgical (MIS) devices to perform various medical diagnostic and/or therapeutic functions or operations. For example, MIS devices find application in cardiac electrophysiology studies and procedures, such as various cardiac diagnostic and/or ablation procedures. In general terms, MIS devices used for ablation procedures typically comprise an elongate shaft having proximal and distal end portions, a handle coupled to the elongate shaft at the proximal end portion, and one or more ablation electrodes or elements mounted on or coupled to the elongate shaft at the distal end portion. The ablation elements may be used to deliver energy to a region of the heart to ablate a site of cardiac tissue that causes, for example, an arrhythmia or abnormality in the heart rhythm.
When performing ablation procedures, the ablating MIS device may be navigated or guided through the vasculature of the patient to the desired ablation site in a number of ways. One exemplary way is to use an imaging modality known as fluoroscopy. In fluoroscopy, a fluoroscope is used to provide practitioners with real-time two-dimensional images of internal anatomic structures of a patient. The fluoroscope further provides a means for monitoring the location and position of medical instruments, such as MIS devices, that are disposed within the patient at locations within the field of view of the fluoroscope. In general terms, a fluoroscope consists of a radiation source (i.e., x-ray source) and a fluorescent screen. In practice, a patient is placed between the radiation source and the screen, and x-rays are directed toward the particular region of the patient's body that is within the field of view of the fluoroscope and that the practitioner wishes to image. As the x-rays pass through or are absorbed by the patient, images are created on the fluorescent screen. The fluoroscope may also include a monitor electrically connected to the screen upon which the images may be displayed for the practitioner to see.
Another way for navigating or guiding an MIS device through the vasculature is to use an ultrasound-based imaging modality known as intracardiac echocardiography (ICE). In such systems, an ICE catheter having an ultrasound transducer mounted thereon, or otherwise associated therewith, is inserted into the patient's body. The ultrasound transducer acquires image data corresponding to internal anatomic structures, which is then used to create two- or three-dimensional models, for example, of a desired region of the patient's anatomy.
These known systems or techniques for navigating or guiding a MIS device in an ablation procedure are not without their drawbacks, however. For instance, each of the navigation or guiding methodologies described above are “offboard,” or separate and distinct components from the ablation tool or MIS device performing the ablation procedure. Accordingly, performance of the procedure is made more difficult by requiring the use of multiple components. Furthermore, each methodology is relatively difficult to master. Another drawback relating particularly to fluoroscopy is that it provides relatively poor anatomic detail due, at least in part, to the two-dimensional images that it creates, making it difficult to determine with a high level of accuracy and precision exactly which tissues may be in the field of view or ablating field of an ablation element. Further, in order to provide useful images in fluoroscopy, the patient is exposed to high doses of radiation, which is undesirable for both the patient and the practitioner performing the procedure or operating the fluoroscope.
When an accurate and sufficiently detailed view of the ablation element and the ablative field are not known, unintended damage may be inflicted on tissue not needing or intended to be ablated, as a result of the practitioner not having the device in the correct position or orientation. Additionally, these known imaging modalities do not provide a sufficient means for monitoring and/or assessing an ablation procedure to verify that the desired tissue has been sufficiently ablated.
Accordingly, there is a need for an ablation tool or MIS device that will minimize and/or eliminate one or more of the above-identified deficiencies.